Cystic fibrosis is an example of a protein folding disorder. It is a hereditary disease caused by mutations in a gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). The CFTR gene encodes a chloride channel that is expressed in multiple epithelial cell types. A common CFTR mutation, delF508, causes the failure of CFTR to traffic correctly to the plasma membrane because of protein misfolding. The delF508 mutation is estimated to account for 90% of mutant alleles. Because of its high degree of incidence in the cystic fibrosis population, delF508-CFTR is a prime target for cystic fibrosis therapeutics. As such, delF508-CFTR has been extensively studied and is a model for the study of protein folding diseases.